mscms: make missing lcms2 an error, not a fixme

[Hans Leidekker]

On Wed, 2014-01-22 at 21:28 -0800, Austin English wrote:
> It breaks applications (e.g., the Adobe Flash installer), it should be an error.

In that case many other fixme's also qualify as errors ;-) Loading mscms without
liblcms2 support doesn't necessarily mean that the application will break. It may
not actually use it or it may only use functions that don't depend on liblcms2.